The invention relates to a support for the plates of filter presses and filters for filtering over a filter wall, for instance over a filter cloth or filter paper, which filter support is advantageously made of plastic material. The draining arrangement of the filter support of the invention comprises regularly oriented projections of geometric shapes.
At present, supports for the plates of filter presses and filters are different types of draining arrangements. As a draining arrangement, a system of projections supporting the filter wall and a system of channels serving for the removal of filtrates between said projections is employed. A commonly used draining arrangement uses vertical grooves at both sides of filter press plates, particularly wooden filter press plates and plates made of polypropylene. Some filter press plates made of plastic materials are also provided with inclined grooves, with cylindrical projections and projections in the shape of truncated pyramids. Another draining arrangement uses truncated pyramids with channels with two different depths for the removal of filtrates.
All of the above-mentioned draining arrangements have the common drawback that the surfaces of the projections on which the filter wall bears is smooth, flat or slightly convex, and the filter wall bears on this surface rather tightly due to the filter pressure. At places where the filter wall is in contact with the projections of the draining arrangement, the speed of filtration is reduced, such reduction being larger the thinner the filter wall is, and the larger the surface of the projections. Recently, thinner, hard and rather dense filter walls are used which are made of synthetic fibers. These walls are smoothed by calendering them from one or both sides in order to make them anti-adhesive to filter cakes. This kind of filter wall requires a particularly effective draining arrangement.